Question

Distinguish between the following: Septal nephridia and pharyngeal nephridium

Answer 1

Hint: The nephridium is formed of an animal tissue matrix having long coiled nephridial duct forming loops. There are four such canals within the straight lobe, which are present three within the lower part and two within the upper part of the limbs of the twisted loop.

Complete step by step answer:

Septal nephridia	Pharyngeal nephridium
The septal nephridia could also be considered typical of all the nephridia of Pheretima.	These nephridia dwell three paired tufts, one on either side of the anterior region of the alimentary tract within the segments 4th, 5th and 6th.
The nephridia hang freely within the coelom and are attached only by their terminal ducts.	The tufts of pharyngeal nephridia also contain blood glands and supply blood.
Each septal nephridium consists of the nephrostome, neck, body of nephridia and therefore the terminal duct.	The pharyngeal gland consists of the many chromophil cells, which produces saliva containing proteolytic enzymes; protease and mucin.
Each septum bears nephridia on both the surfaces arranged in semi-circles around the intestine, two rows ahead of the septum and two behind it.	It has a brief straight lobe and a spirally twisted loop, its lumen has ciliated canals.

Note:
- Uric acid isn't found within the earthworms. However, the amino acids are degraded to make free ammonia and therefore the urea is synthesised within the chloragogen cells which are released into the coelomic fluid and also within the blood for its removal. Free amino acids aren't excreted but traces of creatinine occur within the urine.
- Like other animals, in earthworms also, the protein catabolism leads to the formation of nitrogenous waste substances like certain amino acids, ammonia and urea.